determination of lun misalignment

[bryant]

is the output of the following command:

> dfm perf diagtroubleshoot -a anpdfil1 -d $(( 60 * 60 * 24 ))

    Diagnosis Check Name : LUN Misalignment

   Status : Error

   Observation : Following lun objects has violated LUN Misalignment -SQL_ANMXPQL01_SnapInfo/SnapInfo, SQL_ANTXPQL01_SnapInfo/SystemDatabases,SQL_ANPXTFS1_SnapInfo/SnapInfo, SQL_ANTXPQL01_LOGS/TransactionLog_04,SQL_ANMXPQL01_LOGS/TransactionLog_02, SQL_ANPXTFS1_SnapInfo/SystemDatabases,SQL_ANMXPQL01_LOGS/TransactionLog_03, SQL_ANTXPQL01_SnapInfo/SnapInfo,SQL_ANMXPQL01_SnapInfo/SystemDatabases, SQL_ANPXTFS1_LOGS/Transaction_Logs,SQL_ANMXPQL01_LOGS/TransactionLog_04, SQL_ANTXPQL01_LOGS/TransactionLog_03, SQL_ANTXPQL01_LOGS/TransactionLog_01,SQL_ANMXPQL01_LOGS/TransactionLog_01, SQL_ANTXPQL01_LOGS/TransactionLog_02

    Recommendation : Contact your support engineer.

    Diagnosis Check Name : LUN Partial read/write blocks

   Status : Warning

   Observation : Following lun objects has violated LUN Partial read/write blocks - SQL_ANPXTFS1/Databases,SQL_ANMXPQL01_SnapInfo/SnapInfo, SQL_ANTXPQL01_SnapInfo/SystemDatabases,SQL_ANMXPQL01/Database_04, SQL_ANPXTFS1_SnapInfo/SnapInfo,SQL_ANTXPQL01/Database_01, SQL_ANTXPQL01_LOGS/TransactionLog_04,SQL_ANMXPQL01/Database_03, SQL_ANMXPQL01_LOGS/TransactionLog_02,SQL_ANPXTFS1_SnapInfo/SystemDatabases, SQL_ANMXPQL01_LOGS/TransactionLog_03,SQL_ANTXPQL01_SnapInfo/SnapInfo, SQL_ANMXPQL01_SnapInfo/SystemDatabases, SQL_ANPXTFS1_LOGS/Transaction_Logs,SQL_ANTXPQL01/Database_02, SQL_ANMXPQL01_LOGS/TransactionLog_04,SQL_ANMXPQL01/Database_01, SQL_ANTXPQL01_LOGS/TransactionLog_03,SQL_ANTXPQL01_LOGS/TransactionLog_01, SQL_ANTXPQL01/Database_03,SQL_ANMXPQL01_LOGS/TransactionLog_01, SQL_ANMXPQL01/Database_02,SQL_ANTXPQL01_LOGS/TransactionLog_02, SQL_ANTXPQL01/Database_04

    Recommendation : Configure the host file system to haveblock size in multiples of 4k.

a definitive determination of misalignment (does the command measure starting offset)?

or, is the command merely reporting the existence of partial block writes?

pls. advise...

- charlie

is the output of the following command:

> dfm perf diagtroubleshoot -a anpdfil1 -d $(( 60 * 60 * 24 ))

    Diagnosis Check Name : LUN Misalignment

   Status : Error

   Observation : Following lun objects has violated LUN Misalignment -SQL_ANMXPQL01_SnapInfo/SnapInfo, SQL_ANTXPQL01_SnapInfo/SystemDatabases,SQL_ANPXTFS1_SnapInfo/SnapInfo, SQL_ANTXPQL01_LOGS/TransactionLog_04,SQL_ANMXPQL01_LOGS/TransactionLog_02, SQL_ANPXTFS1_SnapInfo/SystemDatabases,SQL_ANMXPQL01_LOGS/TransactionLog_03, SQL_ANTXPQL01_SnapInfo/SnapInfo,SQL_ANMXPQL01_SnapInfo/SystemDatabases, SQL_ANPXTFS1_LOGS/Transaction_Logs,SQL_ANMXPQL01_LOGS/TransactionLog_04, SQL_ANTXPQL01_LOGS/TransactionLog_03, SQL_ANTXPQL01_LOGS/TransactionLog_01,SQL_ANMXPQL01_LOGS/TransactionLog_01, SQL_ANTXPQL01_LOGS/TransactionLog_02

    Recommendation : Contact your support engineer.

    Diagnosis Check Name : LUN Partial read/write blocks

   Status : Warning

   Observation : Following lun objects has violated LUN Partial read/write blocks - SQL_ANPXTFS1/Databases,SQL_ANMXPQL01_SnapInfo/SnapInfo, SQL_ANTXPQL01_SnapInfo/SystemDatabases,SQL_ANMXPQL01/Database_04, SQL_ANPXTFS1_SnapInfo/SnapInfo,SQL_ANTXPQL01/Database_01, SQL_ANTXPQL01_LOGS/TransactionLog_04,SQL_ANMXPQL01/Database_03, SQL_ANMXPQL01_LOGS/TransactionLog_02,SQL_ANPXTFS1_SnapInfo/SystemDatabases, SQL_ANMXPQL01_LOGS/TransactionLog_03,SQL_ANTXPQL01_SnapInfo/SnapInfo, SQL_ANMXPQL01_SnapInfo/SystemDatabases, SQL_ANPXTFS1_LOGS/Transaction_Logs,SQL_ANTXPQL01/Database_02, SQL_ANMXPQL01_LOGS/TransactionLog_04,SQL_ANMXPQL01/Database_01, SQL_ANTXPQL01_LOGS/TransactionLog_03,SQL_ANTXPQL01_LOGS/TransactionLog_01, SQL_ANTXPQL01/Database_03,SQL_ANMXPQL01_LOGS/TransactionLog_01, SQL_ANMXPQL01/Database_02,SQL_ANTXPQL01_LOGS/TransactionLog_02, SQL_ANTXPQL01/Database_04

    Recommendation : Configure the host file system to haveblock size in multiples of 4k.

a definitive determination of misalignment (does the command measure starting offset)?

or, is the command merely reporting the existence of partial block writes?

pls. advise...

- charlie

[tkettler3560]

We are getting the same message thru Operations Manager GUI.  Diagnosis shows all VMFS LUN's that we created manually as misaligned.  Even though they have the correct starting offset (128) under Vmware.

If we create a new Volume/LUN using Virtual Storage Console (VSC), Operations Manager does not show it as Misaligned.

Why would Operations Manager show a correctly created (we think) LUN as misaligned, just because it was not created thru VSC?

Thanks all for any help or observations.

Tom...

[dgwhitecalgary]

Funny... I just opend a case about the same issue and have not received much feedback from NetApp

[rbalaji]

Hi,

Performance Advisor uses lun:read_align_histo and lun:write_align_histo counters for determining misaligned luns both of which are diag counters provided by ONTAP.

AFAIK, diag counters by definition are not thoroughly tested by ONTAP and are not guaranteed to work for properly in certain cases.

This problem has been identified and we are working with ONTAP team on fixing this counter to be 'basic' from 'diag'

[tkettler3560]

Ok, thank-you!

[bryant]

the reason for my asking is, the message:

"Recommendation : Configure the host file system tohave block size in multiples of 4k."

can be interpreted as diagnosing the presence of lun/vmdk misalignment. ihac that brought this to my attention.

if interpreted this way, this is an incorrect diagnosis of lun misalignment. the existence of partial block writes is not a definitive diagnosis of misalignment.

as to the technical background as to why, check here - http://web.netapp.com/~bryant/Tips-n-Tricks/vmdk_misalignment/index.htm#DetectingtheProblem

- charlie